feat: allow setting schema for connection in postgres (#2777)

This PR introduce a new config for database, `database.schema`, allowing user to specify a specific schema to use for their postgres database connection. As the default value is set, it will be backward compatible.

Related discussion: https://community.vikunja.io/t/postgres-database-has-error-pq-relation-tasks-does-not-exist/1333

Reviewed-on: https://kolaente.dev/vikunja/vikunja/pulls/2777
Co-authored-by: John Doe <hugosum.dev@protonmail.com>
Co-committed-by: John Doe <hugosum.dev@protonmail.com>

pkg/config/config.go

@@ -93,6 +93,7 @@ const (
 	DatabaseSslKey                Key = `database.sslkey`
 	DatabaseSslRootCert           Key = `database.sslrootcert`
 	DatabaseTLS                   Key = `database.tls`
+	DatabaseSchema                Key = `database.schema`
 
 	TypesenseEnabled Key = `typesense.enabled`
 	TypesenseURL     Key = `typesense.url`
@@ -344,6 +345,7 @@ func InitDefaultConfig() {
 	DatabaseSslKey.setDefault("")
 	DatabaseSslRootCert.setDefault("")
 	DatabaseTLS.setDefault("false")
+	DatabaseSchema.setDefault("public")
 
 	// Typesense
 	TypesenseEnabled.setDefault(false)